ADHD Presentations and Severity in Adults: Psychometric Profiles, Psychiatric Comorbidities, and Emotional Dysregulation in Relation to Psychiatric Hospitalization

Background/Objectives: Attention-deficit/hyperactivity disorder (ADHD) in adults is heterogeneous in symptom presentation, severity, and comorbid psychopathology, yet systematic data from Italian clinical populations remain limited. Methods: In this retrospective, cross-sectional study, we analyzed routine clinical data from 219 adults with a DSM-5 diagnosis of ADHD at a specialist mental health service in Milan. We compared psychometric profiles and psychiatric comorbidities across ADHD presentations (Combined vs. Inattentive), examined the associations of clinician-rated ADHD severity with dimensional and categorical outcomes, and explored, in an exploratory cross-sectional indirect-effect analysis, whether emotional dysregulation statistically accounted for the association between ADHD severity and psychiatric hospitalization. Multiplicity was addressed with Holm and false-discovery-rate procedures within predefined families of outcomes. Measures included the Zung Depression Scale, STAI, Difficulties in Emotion Regulation Scale (DERS), Internet Addiction Test, Adult ADHD Quality of Life Scale, Barratt Impulsiveness Scale, and the SCID-5-PD. Analyses comprised MANCOVA, multiple linear and binary logistic regression, and an exploratory indirect-effect analysis (PROCESS Model 4). Results: The Combined presentation was associated with nearly fivefold higher odds of substance use disorder than the Inattentive presentation (robust to Holm correction), whereas the overall multivariate difference in psychometric profiles was not significant and the higher emotional dysregulation in the Combined presentation was a small effect not robust to multiplicity correction. Greater ADHD severity was associated with greater emotional dysregulation and higher odds of substance use disorder (both robust to Holm correction) and, less robustly, with depressive symptoms, problematic internet use, and lower quality of life. A statistically significant cross-sectional indirect association between ADHD severity and hospitalization via emotional dysregulation was observed (indirect effect B = 0.21, 95% CI [0.03, 0.50]); because the temporal ordering of these variables could not be established, this finding does not demonstrate mediation. Female sex was independently associated with lower quality of life and higher depressive symptoms, and higher educational level was associated with lower odds of substance use disorder and hospitalization. Conclusions: These findings, obtained in a specialist clinical sample, support the clinical relevance of assessing ADHD presentation, severity, and emotional dysregulation, and generate hypotheses that require confirmation in prospective, multicentre studies.